Induction-furnace.



, I bv M. UNGER'.

- INDUCTION FURNACE.

AAAAAAAAAAAAAAAAAA Y 6, 1908. 941 435. Patented Nov. 30, 1909.

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AT TY INVENTEIR i M. UNGEB. INDUCTION FURNACE. APPLICATION FILED MAY s, 1908 941,435. j Patented Nov; 30,1909.

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' Witnesses: Inventor:

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men insulin, or rxtrrsrxnnn, massaonusncrrs, ASSIGNOR 'ro smtanaz 'zmncmrc COMPANY, a CORPORATION 0F NEW YORK.

naces,of which the following is a specification.

My invention relates to electric furnaces 1o of-the' type known as induction furnaces,

, which are used for metallurgical purposes. Furnaces of this type,' in general, comprise .aamagnetic core and primary winding u on this core, and a furnace chamber placed in so that the charge will serve as a secondary, that is, the magnetic flux' threading through the charge will induce currents in'the same.

Infurnaces. as heretofore built the size .of

the secondary (that is, the quantity of charge) cannot be increased without greatly reducing the power factor unless the frequency is very low. This, of; course, is due to the fact that as the size of the charge increases there is it results" in a low power factor according to well-known electrical principles. To 'run the furnace atvery low frequencies requires special installations, and such special installations are yery costly. Moreover the power .factor cannot lie' ii'nproved sufliciently by this :means when tie size of the furnace exceeds certainlimits, or when the specific re-' 7 sistance of the-charge is low.

The furnace which formsthe subject of the present invention is soconstructed that a current from ,a single-phase, ora polyphase source, may be used forits operation and not only the advantage incident to using 0 currents from ordinary commercial installations is gained, but also a very marked improvement in power factor. Besides this, my furnace'has a better thermal efficiency than furnaces as built heretofore. Other ad-. vantages, such as convenience of, charging and flexibility of voltage, will be hereinafter further pointed out. I

, Figure 1 shows the furnace in perspect ve; Fig.2 is a plan view of the furnace, showing also current connections to a po'lyphase system; and Fig; 3 shows the connections to be used with a. single-phase source of energy.

F ig. 1 shows a furnace of the tilting type 'with 'a furnace 1 set upon-a base plate 2 6 shown in both Figs. 1- and 2, the furnace INDUCTION-FURNACE.

Specification of Letters Patent. Application filed ma s, 1908. Serial No. 431,138.

I has two sets of primary. windings large stray field, which"- Patentet'l Nev; so, recs.

3 and 4, Wound upon cores 5 and (3. Surrounding these primary windings is the furnace chainher 7 inclosed in fire-brick walls 8. An aliernzttii'ig current passing through the pri-- mary windings 3 induces a current in a charge placed in the furnace chamber according to wellkno wn principles. The lluid metal or flux maybe tapped oil through the spout 10. As shown in the figure, the annular furnace chambers inter-link to form a central space, which, as will be pointed out, forms a most convenient treating chamber. As the an nular channels surrounding the .riinary cores may bemadc of comparativey small cross section without sacrificing the capacity of the furnace, the resistance at these regions will be correspondingly high, thus keeping ayhigh power factor, and at the same time making a furnace of larger capacity than it is now possible to operate with commercial frequencies. As there will be practically no current in the center of the furnace, the

furnace chamber is made shallower at this point by the projection 9. However, the

central chamber holds a considerable amount 1 of the chargc,'which '18 protected in this way .from excessive, radiation,

and the furnace has, therefore, a high thermal eilicicncy.

A point not, to be overlooked is that the 35 central space may be used for the ll'lh'UtlHP- tion of comparatively large blocks of raw material, either ore or flux. As the size of the furnace chamber is confined within narrow limits this matter of convenience of charg- 99 ing forms an important item-in the construc tion of furnaces of this kind.- The. central space may be'used for the refining of metals,

in a manner similar to the open-hearth process. l The furnace is shown in Fig. 9. connected to a transformer supplied with three-phase currents in its primary coils'll, which are 'T-connectcd and deliver two-phase currents in the 56(501l(ll111(:s ]2. With proper connections in the manner well understood by those skilledin the art, the furnace may be voperated on any polyphase system. The two units shown, or any number of units may be operated in parallel on a single-phase sysas illustrated by Fig. 3, in which the primarywindings 3, 4 are connected-in. parallel .to a single-phase source of energy r3,

by conductors 14, 15 respectively. It w1ll be seen that this type'of furnace possessesfla' 110 flexibility of voltage not possih le with other.

types ofsi' le-phase or polyphase furnaces.

What I c aim as new and-desire to secure by Letters Ialent of the United States, is

1. In an lnduction furnace, the combination of a'piurehty of magnetic cores, windings upon sald. cores, and a plural ty of annular furnace chambers surrounding'said cores and communicating with a shallow central. chamber.

2. In an induction furnace, the combination of a plurality of magnetic cores, independent primary windings u on saidcores,

and 21 central treating chem r surrounded, by narrow, segmental annular chambers opening into sold central chamber and in inneti c cores forming closed magnetic circuits Independent primary WlIldlIlgS upon each of ductive relation-with said primary windings. 7 v

3. The combination of a plurality of magsaid cores, :1 single source of energy for said v windings, and a plurality of intereommuhieating charges m inductive relatlon to salgi magnetic circmts.

In testimony whereof, I havehereunfo-set 

